$\dfrac{1}{3} + \dfrac{3}{5} = {?}$
Answer: $ = {\dfrac{1 \times 5}{3 \times 5}} + {\dfrac{3 \times 3}{5 \times 3}} $ $ = {\dfrac{5}{15}} + {\dfrac{9}{15}} $ $ = \dfrac{{5} + {9}}{15} $ $ = \dfrac{14}{15}$